The number of application ranges for magnetic-field sensors is increasingly growing, in particular, in the automotive sector. Magnetic field sensing can be used, inter alia, for non-contact, low-loss and floating measurement of currents. Examples are the determination of electrical operating parameters of generators and electric drives. Generally, currents from the milliampere range to the kiloampere range have to be measured, which requires a measuring range of five to six magnitudes.
The state of the art today is to measure magnetic fields, for example, of electric conductors, using magnetic-field sensors such as Hall sensors, bipolar magnetotransistors, magnetoresistive resistors, lateral magneto-FET structures, etc. A particularly sensitive component is the so-called xe2x80x9clateral magnetotransistorxe2x80x9d whose functioning is based on the asymmetrical current distribution between two bipolar transistors which is generated by the magnetic field.
For currents in the milliampere range, even such components reach the limits of their sensitivity due to the low magnetic fields, typically in the xcexcT range. In the related art, therefore, small magnetic fields are amplified by so-called xe2x80x9cflux concentratorsxe2x80x9d which cause the magnetic fields to be stronger at the location of the magnetic-field sensors by suitably shaping the respective electric conductors or by means of magnetic circuits made of highly permeable materials.
The inventive device for sensing a magnetic field, the inventive magnetic-field sensor and the inventive current sensor have the advantage over the background art that flux-concentrating aids can be dispensed with, which saves costs and reduces the required installation space. This is possible by increasing the sensitivity of the device according to the present invention. In this connection, the linear relation between the measuring signal and the magnetic field to be measured is substantially maintained.
It is particularly advantageous that provision is made for a fourth magnetic-field sensing means and for a fifth magnetic-field sensing means, an output variable of the second magnetic-field sensing means corresponding to an input variable of the fourth magnetic-field sensing means, and an output variable of the third magnetic-field sensing means corresponding to an input variable of the fifth magnetic-field sensing means. Thus, by varying the number of the cascade stages according to the present invention, it is possible to obtain different sensitivities, as required, by the connection in cascade of magnetic-field sensors. In this context, it is particularly advantageous that different magnetic-field sensing means are implemented on a single chip.
Moreover, it is an advantage that the first magnetic-field sensing means is a first lateral magnetotransistor, that the second magnetic-field sensing means is a second lateral magnetotransistor, and that the third magnetic-field sensing means is a third lateral magnetotransistor. In this manner, the sensitivity of LMT (lateral magnetotransistor) sensors can be increased according to the present invention by suitably cascading a plurality of such LMT components. By using the output current of one LMT element, i.e. according to the present invention, for example, one of the two collector currents, as the input current, i.e., according to the present invention, for example, as the emitter current, for a another LMT element, the asymmetry effect of the magnetic field on the current distribution in the LMT can be used several times. In this context, it is an advantage that an LMT sensor is already highly sensitive itself and therefore represents a good starting point for the optimization described herein. Alternatively, the presented increase in sensitivity can also be used for all other components working according to a similar principle, i.e., in which the values of two output variables are changed by a magnetic field.
It is also beneficial that the first output variable is a first collector current, that the second output variable is a second collector current, that the first input variable is the emitter current of the second lateral magnetotransistor, and that the second input variable is the emitter current of the third lateral magnetotransistor. This advantageously allows an increase in sensitivity, the relation between the magnetic field and the measuring signal nevertheless being linear for small magnetic fields.